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This content comes from Closed Captioning that was broadcast along with this program.

>>>finally tonight we all know dogs can be trained to do
amazing things
, but playing doctor? jill rappaport with a story of
medical alert dogs
and how they are saving lives.

>> reporter: k.k. and her dog j.j. are inseparable, but j.j. is more than just a pet. [ barking ]

>>good girl.

>> reporter: she's trained to be an alert and protect k.k. the 7-year-old has a
rare disease
called mastocytosis which causes dizziness, drop in
blood pressure
and other symptoms that mimic a severe
allergic reaction
.

>>when k.k. starts to have a reaction j.j. smells the
chemical reaction
and alerts us.

>> reporter: j.j. never leaves her side, even at school.

>>we have one ex-the tra person, one extra thing looking after k.k. and her senses are well beyond what we are capable of.

>> reporter: medical alert or
service dogs
are used to detect everything from cancer to diabetes. like with k.k.'s friend diane.

>>she lets me know by touching my leg with her nose if my
blood sugar
is too low or getting the too high.

>>you have animals that can sense things from so
far away
that we have no idea they are going on.